My use case: I want a small rescue system embedded in ROM (drivers for CompactFlash in PCMCIA reader, network stack, filesystem salvage tools, some convenient ASCII editor like CED or GoldED, etc.) - the compressed image of such system might easily cross the 1MB (maximum current continuous ROM block).

Quote:

it is always GUI which is the annoying part

Besides error popups you just need 2 or 3 widgets - ROM start address ($1000000 could be the default one), a file selector, maybe additionally a 'tick' to enable the feature. Size can be taken from the rom image size.

I rather expected problems due to possible conflicts with other emulated hardware.